Triaryl phosphate esters

ABSTRACT

Composition and process for certain tris(isopropylphenyl) phosphate esters particularly suited for use as polyvinyl chloride plasticizers.

United States Patent 191 Terhune et al. 1451 Jan. 7, 1975 1 TRIARYL PHOSPHATE ESTERS 3,553155 1/1971 Garrett 260/306 Inventors: F- e Terhune westport, Conn; $576,923 4/1971 Randall et al 260/966 Gordon A. Rampy, Nitro, W. Va.

1731 Assignee: FMC Corporation, New York, NY. 7 Primary Examiner-Lorraine A Weinberger Filed Oct 9 '1973 Assistant Examiner-Richard L. Raymond 21 App! No.5 404,380

52 U.S. c1. 260/966, 260/306 R 1571 ABSTRACT .[51] Int. Cl C071 9/08,'C07f 9/12 I [58] Field 0f Search 260/966 Composition and process for certain tris(isopropylphenyl) phosphate esters particularly suited for use as [56] References Cited polyvinyl chloride plasticizers.

UNITED STATES PATENTS 2.473 612 6/1949 Shuman 260/966 2 Claims, N0 Drawings TRIARYL PHOSPHATE ESTERS This invention relates to improved triaryl phosphate esters and methods for preparing same. More particularly, this invention relates to an improved form of a tris(isopropylphenyl) phosphate prepared from a propylated. phenol reaction mixture and containing a high proportion of metaand paramonoisopropylphenyl radicals.

Triaryl phosphate esters have been widely used as plasticizers for polyvinyl chloride resins. Compounds such as triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate and the like have been used for a number of years. Mixed triaryl phosphates such as mixed alkylphenyl/phenyl phosphates are also known and are disclosed, for example, in US. Pat. Nos. 3,553,155, issued Jan. 5, 1971, to Garrett; 3,071,549, issued Jan. 1, 1963, to Stark; and 3,576,923, issued Apr. 27, 1971, to Randell et al. However, it is always I desirable to provide triaryl phosphates which exhibit an improved plasticizing effect and efficiency when formulated into polyvinyl chloride resin formulations.

1n accordance with the' present invention, there is provided a triaryl phosphate ester of the formula (RO),,PO wherein R represents radicals consisting essentially of:

a. at least 90% by weight monoisopropylphenyl radicals, with the proviso at least 80 percent by weight are a mixture of metaand para-monoisopropylphenyl radicals, the mixture containing at least 50 percent to 90 percent by weightmeta-isopropylphenyl radicals based on the weight of the mixture;

b. to 5 percent by weight phenyl radicals; and

c. 5 to percent. by weight of di-,. or triisopropylphenylradicals. 1 1 Thus, the novel triaryl phosphate esters of the present invention are characterized as having only a very small proportion of phenyl radicals and a very substantial proportionof metaand para-monoisopropylphenyl radicals. Triaryl phosphate esters heretofore produced by the phosphorylation of alkylated, particularly propylated, phenol reaction mixtures have generally contained fairly substantial proportions of phenyl radicals in the final product. The prior art fails to recognize the advantage to be gained by minimizing the presence of phenyl radicals and maximizing the presence of metaor para-monoisopropylphenyl radicals in certain relative proportions to each other.

Nevertheless, it has been found that the novel triaryl phosphate esters of the present invention function as excellent plasticizers and are a significant improvement in that they provide a combination of properties not found in conventional triaryl phosphate esters. The

novel phosphate esters of the present invention have a plasticizer efficiency which compares favorably to the lower molecular weight triaryl phosphates, and, importantly, this efficiency is retained after exposure to high temperatures. They have an extremely lowvolatility; they have excellent flame-retardant characteristics considering the molecular weight and the high proportion of isopropyl groups present; they have a low viscosity, and the heat and light stability of polyvinyl chloride compositions containing the novel triaryl phosphates is excellent. A surprising and advantageous property is that the phosphate plasticizersof the present invention are substantially non-migrating when formulated in polyvinyl chloride compositions. Migration of phosphate plasticizers onto lacquered, varnished or other polymeric surfaces has restricted their utility in some applications.

Moreover, when employedin plastisol formulations, the triaryl phosphates of the present invention markedly improve the viscosity stability, and such formulations exhibit a gel time of about 2 hours at C. This effect is a major improvement over heretofore used phosphate plasticizers for plastisols. It should be also noted that the novel triaryl phosphates of the present invention are also suitable for use as hydraulic fluids, and in this connection they exhibit improved hydrolytic stability and improved compression ignition properties.

The novel triaryl phosphates of the present invention are preferably prepared directly from the reaction mixture produced by partially propylating phenol. Generally, the process involves the propylation of phenol, the isomerization of the propylate and the phosphorylation of a certain distillate fraction obtained from the isomerized propylate.

The propylation is carried out by the Friedel-Crafts reaction using about 10 to 40 percent by weight of propylating agent, based on the weight of phenol, and preferably about 20-25 percent by weight propylating agent is employed. The reaction is carried out preferably with propylene, but 2-propyl chloride or 2-propanol may also be used in accordance with known techniques, as disclosed, for example, in US. Pat. No. 3,576,923. The propylation is carried out generally between about and C and preferably at about 140C. Conventional Friedel-Crafts catalysts may be used. Exemplary are Lewis acids such as aluminum chloride, ferric chloride, stannous chloride, zinc chloride, boron trifluoride, titanium tetrachloride, as well as Bronsted acids as exemplified by sulfuric acid, orthophosphoric acid, p-toluene sulfonic acid, perchloric acid, acid treated Montmorillonite clay and other activated clays and earths.

After the propylation is concluded, the propylated phenol reaction mixture is isomerized by heating and stirring in the presence of a small amount of Lewis or Bronsted acid catalyst. The same catalysts suitable for the alkylation step are suitable in the isomerization step. Preferably, acid treated Montmorillonite clay is used in amount between about 1 .to 5 percent by weight, based on the weight of the reaction mixture, at a temperature of about 200C, preferably about C, for several hours in order to effect isomerization and produce an alkylate havingahigh proportion of monoisopropyl radicals located in the metaand para-positions. i

The isomerized alkylate is then fractionally distilled and only fractions boiling between about 220C and 235C are collected and combined. The combined fractions are then phosphorylated in a conventional manner. The preferred phosphorylation catalyst is aluminum chloride, but other Lewis acid catalysts are suitable. The preferred phosphorylating agent is phosphorus oxychloride, but phosphorus oxybromide 'or phosphoric acid may also be employed. The phosphorylation reaction employs from about 0.05 to 1.5 percent, preferably 1 percent, by weight of phosphorylation catalyst and about 2.5 to 3.5 moles of propylated phenol per mole of phosphorylating agent. The reaction is carried out at 'a temperature between about 100-200C, and preferably by slow addition of the phosphorylating agent at a temperature of 100110C and thereafter increasing the temperature to about 180-190C to complete the reaction. The phosphate ester product is recovered by distilling to obtain a distillate having a monoisopropylphenyl radicals and at least 80 percent,

and preferably at least 85 percent, by weight are mixed metaand para-monoisopropylphenyl radicals. There are present.5 percent dior tri-isopropylphenyl radicals. Less than 5 percent, and preferably less than 1 percent are phenyl radicals. Most preferably, no analyzable (i.e., only traces of) phenyl radicals are present.

The final product contains at least 80 percent of a mixture of monoisopropylphenyl radicals located in the metaand parapositions. Of thesemetaand paraisopropylphenyl radicals, at least 50-90 percent by weight should be meta-isopropylphenyl radicals and 50 to 10 percent are para-isopropylphenyl radicals. The preferred distribution in thismixture is 65 to 75 percent of meta-isopropylphenyl radicals and 35 to 25 percent of para-isopropylphenyl radicals. I

Considering the relatively high molecular weight of the phosphate ester product produced according to the present invention, it has a number of highly desirable properties when formulated into polyvinyl chloride compositions. The plasticizer efficiency is unusually good and the retention of efficiency (modulus-and elongation) after exposure to high temperatures is a substantial improvement over most heretofore used phosphate plasticizers. The plasticized. product has a very low volality which is an important property for many plasticizer applications, such as in vinyl upholstery for use in automobiles. These properties are indicative of improved permanence. Again, considering the presence ofa relatively large number of isopropyl groups, plasticized polyvinyl chloride compositions containing the novel product of the'present invention,

exhibit excellent flame-retardant and improved smokesuppressant qualities.

The novel triaryl phosphateplasticizers of the present invention exhibit an unusual property in that they are'substantially non-migrating plasticizers. When plasticized polyvinyl chloride compositions are placed into contact with other polymeric materials, such as cellulose nitrate or acrylic lacquers, migration of the plasticizer onto these surfaces may occur. Thus, when plasti- I cized polyvinyl chloride articles contact surfaces containing a polymeric coating compatible with the plasticizer, such as lacquered automobile or' furniture surfaces, the migration phenomenon can soften or destroy the surface finish. Migration onto an adhesive surface can weaken the adhesive' bond; rigid polymers can become brittle and cracked as the result of plasticizer mielectrical and telephone wires which frequently come into contact with surfaces which can be adversely affected by plasticizer migration.

Plastisol formulations containing the novel triaryl phosphates produced in accordance with the present invention are a particularly preferred embodiment. Plastisols are dispersionsof finely divideddispersion grade? polyvinyl chloride resin in a plasticizer. [t has been found that plastisol formulations made with the novel products of the present invention exhibit a marked improvement with regard to viscosity stability and at the same time have a desirable rapid cure rate. Thus, standard plastisol formulations (88 phr plasticizer) containing thenovel products of the present invention exhibit gel times at 65C of about 2 hours or more. Polyvinyl chloride plastisols containing heretotion will generally contain from about 30 to 150', preferably to 1.00, parts of plasticizer'per 100 parts polyvinyl chloride resin.

The novel phosphate ester plasticizers of the present invention are employed in conventional quantities in polyvinyl chloride compositions, that is, about 5-150 parts by weight of vplasticizerper 100 parts-of vinyl chloride polymer.

The invention is further illustrated by. the following 1 examples which are not to be considered as limitative of its scope. Parts and percentages are by weight and temperatures are. in degrees centigrade unless otherwise indicated. r

' EXAMPLE] i A 2300 m1 portion of the propylate was isomerized by heating with stirring at 180C for 23 hours in the presence of 46 grams of activated Montmorillonite clay gration. It has been generally recognized that phosphate plasticizers generally exhibited a-more pronounced tendency toward migration, particularly onto lacquered surfaces, when formulated into polyvinyl chloride compositions..The triaryl phosphate plasticizers of the present invention have. been found to exhibit little or no migration and therefore offer an'advantage not available in heretofore employed triaryl phosphate plasticizers. Thus, they are particularly suitable for use in connection withpolyvinyl chloride coverings for catalyst. Percent by-weight analysis of the propylate both before and after isomerization is shown below.

After Before lsomerization lsomerization Phenol 38.0 37.7 Ortho IPP" 34:9 9.9 Meta & Para 13.7 v 42.0 lPP- 2,6 DIP!" 4.0 0.1 2,4 DlPP 7.3 2.4 2,5 & 3,5 DIPP 0.6 7.8 2,4,6 TIP!" 1.4 0.1 2,4,5 TIPP 0.1 0.0

*IPP, DIPP and TIFF represent, respectively. mono-. and tri isopropyl phenol.

The isomerized alkylate'was fractionally distilled at atmospheric pressure and separated into fractions having analyses shown below.

Composition, wt.

600 grams of the combined fractions 4, and 6 were phosphorylated in the presence of 6 grams of Al Cl by adding 210 grams of POCl over a period of 2 hours at 1 C. The temperature was then slowly raised to 180C over a period of 1 hour and held at180C for an additional 2 /2 hours. To complete the reaction, 18 more grams of alkylate were added and the temperature was raised to 190C and maintained at this temperature for 3 more hours.

The 681 grams of crude phosphorylation batch was distilled through a packed column (diameter of 4 inches) at 4 mm. Hg and 265-275C to give 590 grams of product. The product was washed successively with equal volumesof 2 percent NaOH solution and water three times at 80C. The washed product was heated to 120C with 0.5 percent activated carbon and 0.5 percent filter clay and then filtered under vacuum with filter aid. The product has the following properties:

Sp. gr. at /20(. 1.090 (,olor. Pt-(Io (ASTM D4209- Acidity. V: as Acetic Acid (ASTM D-I6l3-61-T) 0.001 Viscosity, cs at 100F 45.2 Free Phenol. (ASTM The product was saponified and by analyzing (vapor phase chromatograph) the recovered phenols the product was found to have the following composition:

Weight Percent Phenol 0.0 Ortho-lPP 7.7 Meta* & Para*-1PP 85.8 2.6 DlPP 0.0 2.4 DlPP 3.5 2.5 & 3,5 DlPP 3.0 2.4.6 TlPP 0.0 2,4,5 TlPP 0.0

100.0 -Total 70% mctaisomer. 3071 paraisomer.

EXAMPLE l1 ison B is an isopropylphenyl phosphate prepared by phosphorylating the alkylate of Example 1 before isomerization, the phosphorylation being carried out in the same manner as described in Example 1. ComparisonC is tricresyl phosphate.

Table 1 Test Method Phosphate Ester Plasticizer Comp. Comp Comp. Prod. of

A B r C Ex. 1

Plasticizer Efficiency- ASTM D 416 2T 100% Modulus (psi) 1475 1727 1528 1846 100% Modulus (psi) Aged 7 days at 100C. 2425 2531 1915 1908 Ultimate Tensile Strength (psi) 2992 2909 2893 2807 Ultimate Elongation 1%) 318 313 290 324 Shore Durometer A Hardness 79 72 79 Loss, Carbon Volatility ASTM D1203- Flame Retardance- ASTM D-2843 Oxygen lndex 29.6 29.6 29.9 28.6

Smoke, Max Density (71) 97 96 93 Smoke Density Rating mi.) 82.3 79.2 79.8 76.5 Migration, lacquer mar ASTM D 2134 66 Softening) Sward Rocker. 24 hours at 75C 53 19.4 33.2 0

Heat Stability -Color 50 (mins.) 17 22 19 25 -Color 500 r r lmins.) 25 31 27 34 Samples 'A" X l X (1.075" thick placed on aluminum plate in forced draft oven ul 177C and a sample removed at regular intervals. Time is noted when samples reach A.P.H.A.' Pt-(u color numher of 50 and 500.

EXAMPLE 111 Comparative properties of these phosphate esters are listed below in Table 2:

Using a dispersion'grade polyvinyl chloride resin, standard plastisol compositions were prepared (88 phr of plasticizer; 1.5 phr barium-cadmium stabilizer.) Gel times are listed in Table 3 below. It is significant that plastisols prepared with the product of this invention exhibit a marked improvement in viscosity stability as indicated by the gel time. A General Electric gel timer was used and the time required to form a thick semi-gel at 65C is measured and recorded in minutes.

a. at least 9 percent by weight monoisopropylphenyl radicals with the proviso that at least 80 percent by weight are-a mixture of metaand paramonoiso- Table 3 Plastisol Data propylphenyl radicals, said mixture containing at Plasticizer v Gel Timc(65C) least 50 percent to 90 percent by weight meta- Pmductof Exampje It 2 minutes as propylphenyl rad1cals,,based on the weight of Comparison 8* 27 minutes 531d mlxture; g p i j v 2 minutes b. 0 to 5 percent by weightphenyl radicals; and

ompar'son mmmes 0.5 to percent by weight dior tri-isopropylphenyl Same plasticizers as used in Example I]. i 10 radicals. I v

v 2. Thephosphate ester of claim 1 wherein there is What is claimed is: present less than 1 percent by weight of said phenyll. A triaryl phosphate ester of the formula (RO) P( radicals. wherein R representsradicals consisting essentially of: I i 

1. A TRIARYL PHOSPHATE ESTER OF THE FORMULA (RO)3PO WHEREIN R REPRESENTS RADICALS CONSISTING ESSENTIALLY OF: A. AT LEAST 90 PERCENT BY WEIGHT MONOISOPROPYLPHENYL RADICALS WITH THE PROVISO THAT AT LEAST 80 PERCENT BY WEIGHT ARE A MIXTURE OF META- AND PARA- MONOISOPROPYLPHENYL RADICALS, SAID MIXTURE CONTAINING AT LEAST 50 PERCENT TO 90 PERCENT BY WEIGHT META-ISOPROPYLPHENYL RADICALS, BASED ON THE WEIGHT OF SAID MIXTURE; B. 0 TO 5 PERCENT BY WEIGHT PHENYL RADICALS; AND C. 5 TO 10 PERCENT BY WEIGHT DI-OR TRI-ISOPROPYLPHENYL RADICALS.
 2. The phosphate ester of claim 1 wherein there is present less than 1 percent by weight of said phenyl radicals. 